(a) Technical Field
The present invention relates to an apparatus and a method for auto-leveling a steering wheel, and more particularly, to an apparatus and a method for auto-leveling a steering wheel capable of automatically aligning the steering wheel and mounting the steering wheel in a vehicle.
(b) Description of the Related Art
In general, a power steering apparatus for steering a vehicle includes a hydraulic power steering apparatus and a motor driven power steering (MDPS) apparatus. More recently, the hydraulic power steering apparatus has been replaced with the MDPS apparatus, and applications of the MDPS apparatus have been increased to include compact vehicles and larger vehicles.
The MDPS apparatus senses a rotation direction of a steering wheel, and a motor rotates a steering shaft or moves a rack bar in a horizontal direction depending on the rotation direction, thereby assisting steering force of a driver.
Meanwhile, the steering apparatus uses a variable gear ratio or a direct steer specification in order to improve steering performance. However, when an assembly of a steering gear and a position of the steering wheel in the vehicle are not accurate, an excessive sense of difference may be caused, thus resulting in a quality problem. In order to solve the above-mentioned problem, it is important to reduce deviation and to set a neutral position of the rack bar and a pinion gear at the time of manufacturing or assembling the steering apparatus.
On the other hand, a reason for using the variable gear ratio or the direct steer specification as described above is that since the steering apparatus should have a small angle of the steering wheel when a large steering such as a change of direction at low and middle speeds is required, and the steering apparatus should not sensitively react according to the angle of the steering wheel around a neutral position in order to give stability at the time of driving in a straight direction at high speed, a teeth shape of the steering gear is varied so that the steering apparatus has a slow steering ratio around the neutral position, but has a fast steering ratio at the time of a large handle steering such as the change of direction, thereby achieving the above-mentioned objects.
Particularly, since a general fixed gear ratio and a variable gear ratio also correspond to an assembly deviation reduction at the time of manufacturing the steering apparatus, missing teeth or a double D type is used at the timing of fastening a gear boxy pinion part and a U-joint (column), and the column and the steering wheel for assembly convenience and the assembly deviation reduction, but in the case of the variable gear ratio having a sharp gear ratio, a minimum tolerance of the missing teeth or the double D type may also cause a problem in performance and quality. That is, the deviation at the time of simply fastening the steering wheel is 10° or more, and in the case in which the steering wheel is distorted as much as 5° or more, the performance problem may occur.
Referring to FIG. 1 (RELATED ART), a sensitivity lean of a driver means that the driver feels as if the vehicle leans due to the assembly deviation of part of the vehicle, although in actuality, the vehicle substantially does not lean. The sensitivity lean has several factors, but among these, an alignment state (hereinafter, referred to as a wheel off center) of a handle of the vehicle, i.e., the steering wheel is the most important factor. In the case in which the wheel off center is distorted, a user feels that the vehicle is not driven in a straight direction. This is the sensitivity lean.
Currently, a wheel off center task is performed in a wheel alignment process. The wheel alignment process includes an upper worker performing the wheel off center and a lower worker performing a wheel alignment adjustment (a tow and a camber). After the upper worker finishes the wheel off center, the lower worker performs the wheel alignment work. The upper worker performs the work using equipment such as a wheel leveler at the time of performing the wheel off center. The wheel leveler has an angle sensor attached thereinto to sense an inclination of a wheel when being attached to the steering wheel and display an angle to an external monitor.
However, according to the related art, since the alignment of the steering wheel (hereinafter, referred to as “wheel off center”) is performed manually by the worker, errors may occur.